demimondaine vs fancy woman

demimondaine and fancy woman both are nouns.

Word	Noun	Adjective	Verb	Adverb
demimondaine	Yes	No	No	No
fancy woman	Yes	No	No	No

As nouns, fancy woman is a hypernym of demimondaine; that is, fancy woman is a word with a broader meaning than demimondaine:

demimondaine (noun)	fancy woman (noun)
a female prostitute	an adulterous woman; a woman who has an ongoing extramarital sexual relationship with a man
	a woman who engages in sexual intercourse for money